Nucl. In 1968, a Soviet team invented the tokamak magnetic confinement device, which demonstrated performance ten times better than alternatives and became the preferred approach. Since then the majority of effort in magnetic confinement has been based on the tokamak principle. Wigbers, M. & Riedmiller, M. A new method for the analysis of neural reference model control. Negative triangularity plasmas are attractive as they have favourable confinement properties without the strong edge pressure gradient typical of H-modes. Computational challenges in magnetic-confinement fusion physics Confining each configuration within the tokamak requires designing a feedback controller that can manipulate the magnetic field6 through precise control of several coils that are magnetically coupled to the plasma to achieve the desired plasma current, position and shape, a problem known as the tokamak magnetic control problem. Lawson, J. D. Some Criteria for a Useful Thermonuclear Reactor (Atomic Energy Research Establishment, 1955). Valid coordinate systems for linearized plasma shape response models in tokamaks. The speed of the waves is chosen to equal roughly the average speed of the electrons in the plasma. MPO supports data collection across distributed parallel streams and learns in a data-efficient way. An early experiment of this type[dubious discuss] in the 1970s was Trisops. The evolution of total plasma current Ip is modelled using a lumped-circuit equation. ADS Our learning framework has the potential to shape future fusion research and tokamak development. 1f). Second, a deep RL algorithm interacts with a tokamak simulator to find a near-optimal control policy to meet the specified goals. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. 3a is courtesy of C. Brandt, IPP. ADS This would require the pinch current to be reduced and the external stabilizing magnets to be made much stronger. Fusion 47, S1S414 (2007); corrigendum 48, 099801 (2008). Fusion 54, 124009 (2012). We also controlled shape and plasma current to their target values, with an Ip RMSE of 1.2kA and shape RMSE of 1.6cm. Open Access Control. You are using a browser version with limited support for CSS. A performance comparison is depicted in Extended Data Fig. We next tested applying auxiliary heating through neutral beam injection to enter H-mode, which is desirable for having higher energy confinement time, but causes notable changes to the plasma properties. These waves can reduce the efficiency or even stop the fusion reaction. Electron heat transport studies. CAS Another established current-drive technique is neutral-beam current drive. Wolf et al 2017 Nucl. The trajectories are shown from the handover at 0.0872s until 0.65s after the breakdown, after which, on shot 70600, the neutral beam heating was turned on and the two shots diverge. This Technical Risk Assessment (TRA) methodology was applied to a deuterium-tritium fuel system for a magnetic-confinement fusion power plant. inProc. We were provided a time-varying trajectory on the basis of the proposed ITER configuration that uses such auxiliary heating. What is Magnetic Confinement? - Definition from Safeopedia We gratefully acknowledge the work and support of the TCV team (see the author list of Codaetal.2) in enabling these experimental results. 3c. Extension of the ECRH operational space with O2 and X3 heating schemes to control tungsten accumulation in ASDEX Upgrade. The interaction trajectories are sampled at random from the buffer by a learner, which executes the MPO algorithm to update the control-policy parameters. With this small neural network, we can perform inference within the L2 cache of the CPU on the control system. Plasma Phys. Plasma-material interactions in current tokamaks and theirimplications for next step fusion reactors. Fusion Sci. Unfortunately, a pulsed reactor would suffer from many engineering problems, such as materials fatigue, and thus other methods have been developed to drive a steady-state current to produce the poloidal magnetic field. In our approach, instead, we only make use of equilibrium reconstruction with LIUQE code10 during post-discharge analysis to validate the plasma-shape controller performances and compute the physical initial conditions for the simulation during training. ISSN 1745-2481 (online) The results suggest that a hydrogen-boron fuel mix has the potential to be used in utility-scale fusion power. J. Fusion Energy 38, 406436 (2019). 8 (IAEA, 2001). Fusion 55, 124012 (2013). Knaster, J. et al. Gerki, S. & De Tommasi, G. ITER plasma current and shape control using MPC. Several baseball series machines were tested and showed much-improved performance. The learning algorithm will automatically adjust input and output layer dimensions for the neural network and will automatically learn a policy suited to the new vessel and control system. The aforementioned characteristics should be readily available, as these are typically part of the design process for a given tokamak. Nucl. Language links are at the top of the page across from the title. The action, that is, the desired coil voltage, is kept constant during these substeps. In the diverted phase (0.55s to 0.8s), the Ip and shape RMSE are 0.28kA and 0.53cm, respectively (0.2% and 2.1%), yielding RMSE across the full window (0.1s to 1.0s) of 0.62kA and 0.75cm (0.47% and 2.9%). The largest such machine was the UK's ZETA reactor, completed in 1957, which appeared to successfully produce fusion. The parameters of this Gaussian distribution over actions are the output of the neural network. A large part of the problem of fusion has been the attainment of magnetic field configurations that effectively confine the plasma. In the late 1950s, Soviet researchers noticed that the kink instability would be strongly suppressed if the twists in the path were strong enough that a particle travelled around the circumference of the inside of the chamber more rapidly than around the chamber's length. The control policy first established a snowflake configuration with X-points separated by 34cm. The program is installing additional tools to optimize tokamak operation and exploring edge plasma and materials interactions. In order to overcome the electrostatic repulsion between the nuclei, they must have a temperature of tens of millions of degrees, creating a plasma. Model-based plasma vertical stabilization and position control at EAST. Reynolds, M. et al. Magnetic confinement of plasmas is the most highly developed approach to controlled fusion. Walker, M. L. & Humphreys, D. A. Plasma Phys. As the normalized pressure p increases to 1.12, seen in Fig. 4c). Preprint at https://arxiv.org/abs/1910.07113 (2019). MagLIF has characteristics of both inertial confinement fusion (due to the usage of a laser and pulsed compression) and magnetic confinement . TCV has a flexible set of magnetic coils that enable the creation of a wide range of plasma configurations. These points are then canonicalized to 32 equally spaced points along a spline, which are the targets that are fed to the policy. Therefore we created a deployment system that compiles our neural network into real-time-capable code that is guaranteed to run within this time window. By the late 1950s, it was clear that plasma turbulence and instabilities were problematic, and during the 1960s, "the doldrums", the effort turned to a better understanding of plasma physics. This has been corrected in the online versions 16 June 2016. As a power-producing machine, the mirror appeared to be a dead end. In 1997, scientists at the Joint European Torus (JET) facilities in the UK produced 16 megawatts of fusion power. Finally, we demonstrate control of a configuration with several plasma droplets in the vessel simultaneously. We set two different values for the droplet \({\sigma }_{\parallel }\) components. This book covers the principles and practices behind the Magnetic Confinement Fusion (MCF) approach to driven new source of energy. 3b, the plasma position and current were maintained accurately, with an Ip RMSE of 2.6kA and shape RMSE of 1.4cm. In a simple straight magnetic field, the plasma would be free to stream out the ends. For example, when the current in the active coils changes polarity and the controller requests a too low voltage, the power supplies can get stuck, erroneously providing zero output current over an extended period of time (Extended Data Fig. If the plasma energy loss is too large, then ignition cannot be achieved. 108, 245002 (2012). The vessel is 1.5m high, with minor radius 0.88m andvessel half-width 0.26m. h, A cross section of the vessel and plasma, with the important aspects labelled. Fusion Physics | IAEA - International Atomic Energy Agency All of our experiments have several objectives that must be satisfied simultaneously. bcomparison between using various amounts of actors for stabilizing a mildly elongated plasma. Nuclear fusion is an important option for a clean and safe solution for our long-term energy needs. 123, 468472 (2017). 1h). Magneto-Inertial Fusion | SpringerLink We test control of droplets, a configuration in which two separate plasmas exist within the vessel simultaneously. 71, 15491552 (1993). First, from the handover at 0.0872s, takeover and stabilize Ip at 110kA. This arrangement generated a field that extended only part way into the plasma, which proved to have the significant advantage of adding "shear", which suppressed turbulence in the plasma. Hommen, G. D. et al. Berkenkamp, F., Turchetta, M., Schoellig, A. Greenwald, M. et al. Measurement of the electron temperature by Thomson scattering in tokamak T3. This stochastic policy is represented by a diagonal Gaussian distribution over coil actions. Nuclear fusion requires very high temperatures that no known material can tolerate, and magnetic confinement is used to prevent the superheated . It uses a combination of two magnetic fields to confine and control the plasma. The tungsten divertor experiment at ASDEX Upgrade. developed the physics simulations. The stellarator and RFP are much like the tokamak. Where relevant, we plot the elongation , the neutral beam heating, the triangularity and the vertical position of the bottom X-point ZX and its target. IEEE Trans. It can, for example, avoid limitations in the power supplies that occasionally cause stuck control-coil currents when reversing polarity (Extended Data Fig. A lower hybrid current drive system for ITER. 129, 152157 (2018). The remaining authors declare no competing interests. 4b), in contrast to existing control architectures that typically assume a strict separation. UK Magnetic Fusion Research Programme This research area covers the UK Atomic Energy Agency (UKAEA) UK Magnetic Fusion Research Programme. Phys. B.T., F.C., F.F., J.B., J.D., M.N., M.R., R.H. and T.E. Extended traces for these shots can be found in Extended DataFig. J. Fusion Energy 39, 123155 (2020). It will squeeze the plasma so that fusion can take place. Nature (Nature) Electromagnetic waves are injected into the plasma so that they propagate within the plasma in one direction around the torus. Injecting impurities heavier than the plasma particles into the plasma and power exhaust region (the Divertor) is crucial for cooling the plasma boundary without affecting the fusion performance. The plasma is, in turn, modelled by the GradShafranov equation21, which results from the balance between the Lorentz force and the pressure gradient inside the plasma on the timescales of interest. B. inThe Future of Helium as a Natural Resource (eds Nuttall, W. J., Clarke, R. & Glowacki, B. Then, a set of independent, single-input single-output PID controllers is designed to stabilize the plasma vertical position and control the radial position and plasma current, all of which must be designed to not mutually interfere6.